Environment Phases

[Mumfrey]

• Add arbitrary phase support to facilitate required feature additions
  • [x] Arbitrary phases and phase providers
  • [x] Refactor launch handler logic from tweaker into new manager object
  • [x] Refactor launch handlers into "platform handlers"
  • [x] Reconfigure startup process to accommodate new phase architecture
  • [x] Add phase criteria objects and phase designators
  • [x] Refactor mixin configs to declare their phase using designators instead of having it added externally
  • [ ] Fix launch
  • [x] Prune initphase branch

[Mumfrey]

This feature will resolve #69